Transmission

ABSTRACT

The present invention relates to a transmission having a housing, having a first drive output shaft, having a second drive output shaft and having a clutch system for distributing a torque between the drive output shafts. At least two transmission components are operatively connected between the drive output shafts and generate lubricating oil pressure. A separate tube extends within the housing from the at least two transmission components to the clutch system in order to supply lubricating oil to the clutch system.

The present invention relates to a transmission having a housing, a first output shaft, a second output shaft as well as a clutch system for the distribution of a torque between the output shafts, wherein at least two transmission components are operatively connected between the output shafts and generate lubrication oil pressure.

Transfer cases are used in all-wheel drive vehicles for the distribution of the torque to a plurality of axles. The distribution takes place by a multi-disk clutch which is made such that the torque transmission between a first output shaft and a second output shaft can be controlled. On engagement by means of a controllable multi-disk clutch, one speaks of “torque on demand”.

The lubrication of transfer cases whose multi-disk clutch above all has a high cooling oil requirement in slip operation usually requires a separate oil supply. In addition, in particular on a blocking of the multi-disk clutch, the bearings which support the components of the multi-disk clutch are fully loaded, with the friction between the bearings and the components being at a maximum.

EP 0 268 904 B1 describes a transfer case in accordance with the preamble of the independent claim. The transmission of EP 0 268 904 B1 has a pump-less oil lubrication of a planetary gearset, wherein gears act as an oil pump to build up a specific pressure and wherein the lubrication oil is supplied to the planetary gearset through a passage and a gap between concentric shafts. The passage is integrated in the transmission housing. The transmission of EP 0 268 904 B1 thus does not have any direct oil lubrication of the multi-disk clutch and requires a complex and/or expensive housing design to form the passage.

It is the object of the present invention to provide a transmission having improved efficiency, a simpler structure and improved oil lubrication properties.

This object is satisfied by the features of claim 1.

Since the transmission of the invention delivers a pump-less oil lubrication, the transmission does not require any additional oil pump. In addition, the direct oil lubrication of the multi-disk clutch and of the supporting bearings improves the efficiency, in particular when the components are temperature loaded. The separate pipe additionally extends within the housing without the necessity of integrally forming a passage in the transmission housing. The transmission housing is simpler in this manner and requires less material and is thus lighter and cheaper.

Advantageous embodiments of the invention are described in the description, in the drawing and in the dependent claims.

In a first preferred embodiment of the invention, the pipe is coupled to the clutch system via a distributor element, with the distributor element conducting lubrication oil between the parts of the clutch system. The components of the clutch system are thus lubricated directly to improve the efficiency.

In a second preferred embodiment of the invention, one of the transmission components is a gear having cut-outs which are provided at at least one side surface of the gear. The lubrication oil is conducted through the cut-outs into the toothed arrangements of the gear to increase the lubrication oil pressure and thus to improve the lubrication oil supply.

In a third improved embodiment of the invention, a lubrication oil shield plate is provided which shields the transmission components with respect to the lubrication oil. The lubrication oil shield plate prevents the respective transmission components from permanently churning in the oil sump, whereby churning losses are reduced to a minimum. The temperature of the lubrication oil is reduced in this manner and the service life of the lubrication oil is extended. In addition, the viscosity of the lubrication oil is maintained for the better lubrication of the clutch system.

In a fourth preferred embodiment of the invention, a lubrication oil supply is provided with a pan, with the pan having a lubrication oil reservoir. The lubrication oil reservoir delivers additional lubrication oil to the transmission components.

The invention will be described in the following only by way of example with reference to the drawings; in which are shown:

FIG. 1 a schematic representation of a motor vehicle powertrain equipped with a transfer case;

FIG. 2 a first sectional representation of a first embodiment of the transfer case;

FIG. 3 a second sectional representation of the first embodiment of the transfer case;

FIG. 4 a perspective representation of a housing, of a gear and of a first embodiment of an oil shield plate of the transfer case;

FIG. 5 a perspective representation of the housing, of the gear and of a second embodiment of the oil shield plate of the transfer case;

FIG. 6 a perspective representation of a third embodiment of the oil shield plate;

FIG. 7 a perspective representation of a fourth embodiment of the oil shield plate;

FIG. 8 a perspective representation of a fifth embodiment of the oil shield plate;

FIG. 9 a sectional representation of a second embodiment of a transfer case;

FIG. 10 a perspective representation of a housing, of a gear, of an output shaft and of a clutch lubrication arrangement of the second embodiment of the transfer case;

FIG. 11 a perspective representation of a lubrication oil supply of the clutch lubrication arrangement of FIG. 10;

FIG. 12 a sectional representation of a first embodiment of the clutch lubrication arrangement of FIG. 10; and

FIG. 13 a sectional representation of a second embodiment of the clutch lubrication arrangement of FIG. 10.

A schematic representation of a vehicle powertrain 10 is shown in FIG. 1 which includes a drive 12 which includes a first power transmission path 14, a second power transmission path 16, an internal combustion engine 18, a manual transmission 20 and a transfer case 22. The internal combustion engine 18 generates a driving torque which drives the transfer case 22 via the manual transmission 20. The transfer case 22 distributes the output torque of the manual transmission between the first and second power transmission paths 14, 16.

The first power transmission path 14 includes a Cardan shaft 24 which is driven by the transfer case 22 and a pair of half-shafts 26 which is connected to a pair of wheels 28 as well as a differential unit 30 which is operative to transmit a driving torque from the Cardan shaft 24 to one or both half-shafts 26. In a similar manner, the second power transmission path 16 includes a Cardan shaft 32 which is driven by the transfer case 22 and a pair of half-shafts 34 which is connected to a pair of wheels 36 as well as a differential unit 38 which is operative to transmit a driving torque from the Cardan shaft 32 to one or both half-shafts 34.

A control unit 40 controls the operation of the transfer case 22 on the basis of a plurality of vehicle parameters. The control unit 40 is electronically connected to at least one sensor and preferably to a plurality of further sensors. Exemplary sensors include a yaw rate sensor 42 and/or wheel speed sensors 44. The sensors 42, 44 detect a plurality of operating states, e.g. the yaw rate of the vehicle, the speed of each wheel and/or the speed of the vehicle. The control unit 40 processes the signal or signals and generates a control signal, with at least one actuator of the transfer case 22 being controlled on the basis of the control signal to distribute a torque between the power transmission paths 14, 16.

The components of a first embodiment of the transfer case 22 will now be described with reference to FIG. 2 and FIG. 3. The transfer case 22 includes a transmission housing 50, a first output shaft 52, a second output shaft 54, a multi-disk clutch 56, an actuator 58 and torque transmission components 60, 62, 64. The first output shaft 52 rotates around a first axis A and is driven directly by an output shaft, not shown, of the manual transmission 20. The second output shaft 54 rotates around a second axis B. The multi-disk clutch 56 is controllable to control a torque transmission between the first output shaft 52 and the second output shaft 54.

The transfer case 22 furthermore includes a clutch lubrication arrangement for the lubrication of the components of the multi-disk clutch 56 and of the supporting bearings. The clutch lubrication arrangement has a pressure chamber 66 integrally shaped in the transmission housing 50, a pipe 68 and a distributor element 70. The pipe 68 extends from the pressure chamber 66 to the multi-disk clutch 56 to supply lubrication oil from the pressure chamber 66 to the multi-disk clutch 56. The distributor element 70 conducts the lubrication oil to the different components and to the supporting bearings of the multi-disk clutch 56. The transfer element 70 in particular includes a plurality of openings 71 which distribute the supplied lubrication oil in different directions. The pipe 68 is preferably shaped of plastic and the distributor element 70 is preferably an injected molded part. As FIG. 3 shows, converging free spaces are formed with a spacing X and Y respectively in each case between the idler gear 64 and the gear 62 as well as the transmission housing 50. The spacings converge in the direction of rotation of the respective gear and serve to regulate the lubrication oil conveying amount. The converging free spaces in particular act as nozzles to increase the lubrication oil pressure.

The torque transmission takes place by the torque transmission components which include a first gear 60, an idler gear 62 and a second gear 64. The first gear 60 is rotationally fixedly connected to a component of the multi-disk clutch 56 and is rotationally journaled around the first output shaft 52. The second gear 64 is rotationally fixedly connected to the second output shaft 54. The idler gear 62 is rotationally journaled within the transmission housing 50 and meshes with each of the first and second gears 60, 64. The idler gear 62 and the second gear 64 dip partly into the lubrication oil which is located in the transmission housing and whose level is indicated by the line SN.

With respect to FIG. 2, the multi-disk clutch 56 includes a clutch hub 73 which is rotationally fixedly connected to the first output shaft 52. The clutch hub 73 can be coupled with friction locking via respective friction disks 72 to a clutch basket 74 which is rotationally journaled around the first axis A of the multi-disk clutch 56 or of the first output shaft 52. The friction locking for the transmission of a torque between the clutch hub 73 and the clutch basket 74 is effected by means of a pressure plate 76 which is axially displaceable against the pre-stress of a plate spring arrangement 78 and hereby presses the respective friction disks 72 of the clutch hub 70 and the clutch basket 74 toward one another.

To selectively displace the pressure plate 76 against the pre-stress and to hereby actuate the multi-disk clutch 56, the actuator 58 includes a support ring 80 and an adjustment ring 82 which are arranged coaxially to one another and with respect to the axis A. The support ring 80 is rotationally fixed and held fixedly axially. For this purpose, the support ring 80 is supported at the first output shaft 52 or a section 88 by means of a radial bearing 84 and of an axial bearing 86 and the support ring 80 is held rotationally fixedly by shape matched connection to a securing section of the transmission housing (not shown). The adjustment ring 82 is rotationally and axially displaceably journaled and it is supported at the pressure plate 76 by means of an axial bearing 90.

The support ring 80 and the adjustment ring 82 each have a plurality of ball grooves 92 and 94 respectively at the mutually facing sides. Said ball grooves extend along the respective peripheral direction with respect to the axis A. A respective ball groove 92 of the support ring 80 and a ball groove 94 of the adjustment ring 82 stand opposite one another and hereby each surround an associated ball 96. The ball grooves 92, 94 are inclined with respect to the normal plane of the axis A, i.e. the ball grooves 92, 94 have a varying depth along the named peripheral extent. It is hereby achieved that a rotational movement of the adjustment ring 82 relative to the rotationally fixedly held support ring 80 results in an axial displacement of the adjustment ring 82 so that the pressure plate 76 is axially offset by such a rotational movement of the adjustment ring 82 and the multi-disk clutch 56 can hereby be actuated. The pre-stress effected by the plate spring arrangement 78 in this respect ensures that the respective ball 96 remains captured in the associated ball grooves 92, 94 in every rotational position of the adjustment ring 82 relative to the support ring 80.

To be able to bring about the explained rotational movement of the adjustment ring 82, it is coupled to an electric drive motor 100 via a gear drive 98. A toothed segment 102 which is made as an angular segment is shaped radially outwardly along a angular range of approximately 90° at the adjustment ring 82. This toothed segment 102 forms, together with a worm gear 104 of the drive motor 100, the gear drive 98. The teeth of the toothed segment 102 of the adjustment ring 82 can have a pitch angle with respect to the axis A of between 5° and 15°, for example. An axis C of the helical gear shaft 104 of the drive motor 100, on the one hand, and the axis A or the axis of rotation of the adjustment ring 82 with the toothed segment 102, on the other hand, intersect one another and form an axial angle of 90°.

The actuation of the shown multi-disk clutch 56 for the transmission of the torque between the first output shaft 52 and the second output shaft 54 takes place as follows:

By actuation of the drive motor 100, a corresponding rotational movement of the worm gear 104 around the axis C is effected. This results due to the gear drive 98 in a rotational movement of the adjustment ring 82 around the axis A. The slanted position of the teeth of the toothed segment 102 of the adjustment ring 82 is in this connection aligned such that the axial forces of the helical gear pair caused by the slanting toothed arrangement on the adjustment rig 82 in the direction of the desired movement of the adjustment ring 82 act to bring about the pressing actuation of the multi-disk clutch 56. The cooperation of the ball grooves 94 of the adjustment ring 82 via the respective ball 96 with the associated ball groove 92 of the support ring 80 has the effect during the rotational movement of the adjustment ring 82 that the adjustment ring 82 moves away axially from the support ring 80 and displaces the pressure plate 76 axially against the bias of the plate spring arrangement 78. The respective friction disks 72 of the clutch hub 70 and the clutch basket 74 are hereby pressed toward one another such that an increasing torque can be transmitted from the clutch hub 70 to the clutch basket 74. The release of the friction locking hereby effected takes place in the reverse order, i.e. the drive motor 100 causes the adjustment ring 82 to make a rotational movement in the reverse sense, with the corresponding axial movement of the adjustment ring 82 and the pressure plate 76 being supported in the direction of the support rig 80 by the plate spring arrangement 78.

On the torque transmission by the multi-disk clutch 56, the first gear 60 rotates around the axis A and drives the idler gear 62. The idler gear 62 thus drives the second gear 64 around the axis B. Normally, the gears 62, 64 have the direction of rotation reproduced by the arrows so that their portions dipping into the lubrication oil sump move with respect to one another. Pressure is generated in the toothed engagement by the conveying effect of the gears 62, 64 to effect a conveying of the lubrication oil via the pressure chamber 66, the pipe 68 and the distributor element 70 up to and into the actuator and the multi-disk clutch. In this connection, the components of the actuator 58, in particular the supporting bearings 84, 86, 90, and the components of the multi-disk clutch 56 are directly lubricated.

As FIG. 4 shows, radially extending cut-outs 122 are provided in an end face 120 of the idler gear 62. Furthermore, a lubrication oil shield plate 124 is provided which approximately surrounds the lower half of the idler gear 62. The pan-shaped lubrication oil shield plate 124 has side walls 126 and a peripheral section 128 between the side walls 126 and serves for the reduction of temperature development and for the regulation of the lubrication oil conveying amount. The lubrication oil shield plate 124 in particular prevents the idler gear 62 from constantly churning in the oil sump in the transfer case 22. An unwanted foaming of the lubrication oil is hereby caused and the resulting churning losses result in an unwanted temperature increase specifically in the higher speed range and thus have to be reduced to a minimum.

In the embodiment of the lubrication oil shield plate shown in FIG. 4, openings 128 are provided in the side walls 126, with lubrication oil flowing in via a curved elongate hole 130 which is formed in the side wall 126 and being conducted into the toothed arrangement of the gears via the cut-outs 122. In another embodiment shown in FIG. 5, the elongate holes 130 a are formed at the edge between the side walls 126 a and the peripheral section 128 a. The lubrication oil shield plate 126 a includes additional openings 132 a which serve for the holding tight of the lubrication oil shield plate 126 a within the transmission housing 50, with the openings 132 a taking up projections, not shown, of the transmission housing 50.

FIGS. 6 to 8 show additional embodiments of the lubrication oil shield plate. The lubrication oil shield plate 124 b of FIG. 6 is similar to the lubrication oil shield plate 124 a of FIG. 5, but the elongate holes 130 b are formed at the bottom between the side walls 126 b and the peripheral portion 128 b, with the elongate holes 130 b lying completely within the lubrication oil sump. The lubrication oil shield plate 124 c of FIG. 7 is similar to the lubrication oil shield plate 124 of FIG. 4, but made without openings in the side walls 126 c. The lubrication oil shield plate 124 d of FIG. 8 is similar to the lubrication oil shield plate 124 b of FIG. 6. Instead of openings in the side walls 126 d, however, an opening 130 d is provided in the peripheral section 128 d.

The components of a second embodiment of a transfer case 22′ will now be described with reference to FIG. 9 and FIG. 10. The transfer case 22′ includes a transmission housing 50′, a first output shaft 52, a second output shaft 54′, a multi-disk clutch 56′, an actuator 58′ and torque transmission components 60′, 62′, 64′. The first output shaft 52′ rotates around a first axis A′ and is driven directly by an output shaft, not shown, of the manual transmission 20. The second output shaft 54′ rotates around a second axis B′. The multi-disk clutch 56′ is controllable to control a torque transmission between the first output shaft 52′ and the second output shaft 54′. In accordance with the second embodiment, the transfer case 22′ is made as a chain gear, with the torque transmission component including gears 60′, 64′ which are rotationally operatively connected by a chain 62′. The chain 62′ has a plurality of chain links 140 which form teeth 142 (FIGS. 12 and 13). The teeth 142 mesh with the teeth of the gears 60′, 64′. The multi-disk clutch 56′ and the actuator 58′ each include components like the multi-disk clutch 56 and the actuator 58′ respectively.

With reference to FIGS. 10 to 13, the transfer case 22′ furthermore includes a clutch lubrication arrangement 150 for the lubrication of the components of the multi-disk clutch 56′ and of the supporting bearings. The clutch lubrication arrangement 150 has a lubrication supply 152 and at least one pipe 154 a, 154 b. Although it is not shown, the clutch lubrication arrangement 150 can furthermore have a distributor element which distributes the supplied lubrication oil in different directions. The lubrication oil supply 152 is preferably an injection molded part and has a pan 156 having two arms 158 extending laterally. The pan 156 includes side walls 160, end walls 162, 162′ and a base 164. The side walls 160 as well as the arms 158 form a chain path 165 through the chain 64′ runs. The arms 158 and an arcuate surface 166 of the end wall 162′ form a pocket which partly includes the gear 60′.

The lubrication oil collects within the trough 156, whereby an additional lubrication oil sump is formed. The base 164 includes passages, not shown, through which lubrication oil is supplied to the chain 62′. The pan 156 has the task of catching the lubrication oil drawn up from the lubrication oil sump by the chain 62′ and of immediately supplying it to the chain 62′ again. That lubrication oil is thus captured again which is not immediately conveyed into the multi-disk clutch 56′ through the pipe 154, 154 b. The pan 156 thus serves for the improvement of the conveying power of the transfer case 22′.

In a first embodiment of the clutch lubrication arrangement 150, a passage 170 is formed through the end wall 162′ and the surface 166. The pipe 154 a is connected to a connection pipe 172 (FIG. 12) to establish flow communication between the lubrication oil supply 152 and the multi-disk clutch 56′ and the actuator 58′. In a second embodiment of the clutch lubrication arrangement 150, a passage 174 is formed by an arm 158 with the pipe 154 a being connected to a connection pipe 176 to establish flow communication between the lubrication oil supply 152 and the multi-disk clutch 56′ and the actuator 58′.

The chain 62′ carries lubrication oil upwardly out of the lubrication oil sump within the transfer case 22′. Normally, the gear 60′ and the chain 62′ have the direction of rotation reproduced by the arrows. Pressure is generated in the tooth engagement region ZB by the conveying effect of the gear 60′ and of the chain 62′ to effect a conveying of the lubrication oil via the pipe 154 a and/or the pipe 154 b up to and into the actuator 58′ and the multi-disk clutch 56′. In accordance with the first embodiment of the clutch lubrication arrangement 150, the lubrication oil is conducted through the passage 170 and the connection pipe 172 up to the pipe 154 a. In accordance with the second embodiment of the clutch lubrication arrangement 150, the lubrication oil is conducted through the passage 174 and the connection pipe 176 up to the pipe 154 b.

Since the transfer case 22, 22′ of the invention provides a pump-less oil lubrication, the transfer case 22, 22′ does not require any additional oil pump. In addition, the direct oil lubrication of the multi-disk clutch 56, 56′ and of the supporting bearings improves the efficiency, in particular when the components are temperature loaded. Individual parts of the oil lubrication system, for example the pipe 68, 154 a, 154 b, the distributor element 70 and the lubrication oil supply 152, can be made of plastic. The parts are thus easy and cheap to make. In addition the pipe 68, 154 a, 154 b extends within the housing 50, 50′ without the need of forming a passage integrally in the transmission housing.

REFERENCE NUMERAL LIST

-   10 vehicle powertrain -   12 drive -   14, 16 power transmission path -   18 internal combustion engine -   20 manual transmission -   22, 22′ transfer case -   24, 32 Cardan shaft -   26, 34 half-shafts -   28, 36 wheels -   30, 38 differential unit -   40 control unit -   42, 44 sensors -   50, 50′ transmission housing -   52, 52′, 54, 54′ output shaft -   56, 56′ multi-disk clutch -   58, 58′ actuator -   60, 60′, 64, 64′ gear -   62 idler gear -   62′ chain -   66 pressure chamber -   68, 154 a, 154 b pipe -   70 distributor element -   71 opening -   72 friction disks -   73 clutch hub -   74 clutch basket -   76 pressure plate -   78 plate spring arrangement -   80 support ring -   82 adjustment ring -   84, 86, 90 bearing -   88 portion -   92, 94 ball groove -   96 ball -   98 gear drive -   100 drive motor -   102 toothed segment -   104 worm gear -   120 end face -   122 cut-outs -   124, 124 a-d lubrication oil shield plate -   126, 126 a-d side walls -   128, 128 a-d peripheral section -   130, 130 a-d elongate hole/opening -   132 a-d opening -   140 chain links -   142 teeth -   150 clutch lubrication arrangement -   152 lubrication oil supply -   156 pan -   158 arms -   160 side walls -   162, 162′ end walls -   164 base -   165 chain path -   166 surface -   170, 174 passage -   172, 176 connection pipe 

1. A transmission comprising: a housing; a first output shaft; a second output shaft; a clutch system for distributing a torque between the output shafts; at least two transmission components operatively connected between the output shafts that generate lubrication oil pressure; and a separate pipe extending within the housing from the at least two transmission components to the clutch system to supply lubrication oil to the clutch system.
 2. The transmission in accordance with claim 1, wherein the pipe is made of plastic.
 3. The transmission in accordance with claim 1, wherein the pipe is coupled to the clutch system via a distributor element, the distributor element conducting lubrication oil between parts of the clutch system.
 4. The transmission in accordance with claim 3, wherein the distributor element is made such that the lubrication oil lubricates circumjacent bearings and friction disks of the clutch system.
 5. The transmission in accordance with claim 3, wherein the distributor element is an injection molded part.
 6. The transmission in accordance with claim 1, wherein one of the transmission components is a gear having cut-outs which are provided at least one side surface of the gear, the lubrication oil being conducted through the cut-outs into the toothed arrangements of the gear.
 7. The transmission in accordance with claim 6, wherein the cut-outs extend in a radial direction.
 8. The transmission in accordance with claim 1, further comprising a lubrication oil shield plate that shields one of the transmission components from the lubrication oil.
 9. The transmission in accordance with claim 8, wherein the lubrication oil shield plate includes side walls and a peripheral section between the side walls.
 10. The transmission in accordance with claim 8, wherein the lubrication oil shield plate has at least one opening that provides a defined lubrication oil supply.
 11. The transmission in accordance with any claim 8, wherein the lubrication oil shield plate is pan-shaped and at least partly surrounds one of the two transmission components.
 12. The transmission in accordance with claim 1, wherein the transmission components include a gear and a chain.
 13. The transmission in accordance with claim 12, wherein the gear and the clutch system rotate around the same axis.
 14. The transmission in accordance with claim 12, further comprising a lubrication oil supply having a pan that partly surrounds the gear and through which the chain extends, the pan having a lubrication oil reservoir.
 15. The transmission in accordance with claim 14, wherein the separate pipe extends from the lubrication oil supply to the clutch system.
 16. The vehicle having the transmission of claim
 1. 17. A transmission comprising: a housing; a pressure chamber having a lubricant therein formed in said housing; a pair of output shafts rotatably supported by said housing; a clutch assembly disposed between said pair of output shafts; a first torque transmitting component disposed between said output shafts; and a lubrication oil shield having a lubricant therein at least partially surrounding said at least one torque transmitting component.
 18. The transmission of claim 17, further comprising a lubrication pipe providing said lubricant from said pressure chamber to said clutch assembly.
 19. The transmission of claim 18, wherein rotation of said first torque transmitting component conveys said lubricant from said pressure chamber through said pipe to said clutch assembly.
 20. The transmission of claim 17, wherein said oil shield includes a pair of sidewalls and at least one opening formed in one of said sidewalls.
 21. The transmission of claim 17, wherein said first torque transmitting component is a gear.
 22. The transmission of claim 17, wherein said lubrication pipe includes a distribution element at an end adjacent said clutch assembly.
 23. The transmission of claim 20, wherein said oil shield includes a plurality of openings.
 24. The transmission of claim 19, wherein said oil shield is operable to prevent churning of said lubricant during rotation of said first torque transmitting component.
 25. The transmission of claim 17, further comprising a second torque transmitting component coupled to said first torque transmitting component. 